Here is a list of numbers to call for any type of help or customer support for Canada Post. I noticed that their link off of Google just brings you to their lame e-mail contact form. So, here they all are, all on one page:

Canada Post General Information: 1-866-607-6301 (Available Monday-Friday 8AM<->6PM local time)

General Canada Post Information Outside of Canada: 1-416-979-8822